Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$229.55	6.595%	$244.6888	$244.69	$244.70	$244.70
Purchase #2	$208.97	6.540%	$222.6366	$222.64	$222.65	$222.60
Purchase #3	$231.73	12.845%	$261.4957	$261.50	$261.50	$261.50
Purchase #4	$196.67	3.229%	$203.0205	$203.02	$203.00	$203.00
Purchase #5	$78.97	13.847%	$89.905	$89.91	$89.90	$89.90
Purchase #6	$121.82	6.351%	$129.5568	$129.56	$129.55	$129.60
Purchase #7	$106.40	4.623%	$111.3189	$111.32	$111.30	$111.30
7 purchase totals =	$1,174.11		$1,262.6223	$1,262.64	$1,262.60	$1,262.60